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OK so here is the concept to take the rise (difference between the measurements between the root and tip) over run (the distance between the two measurements) = m
"If you have a line of slope m, and θ is the angle it makes with the x-axis, then tan(θ) = m. So you can use tan^-1(m), the inverse tangent (sometimes written as the arctangent, "arctan(m)"), to find the degree measure.
This is because if you draw a right triangle from the angle, the rise/run ratio is the same as the side opposite of the angle divided by the adjacent side. This is the tangent function in trigonometry.
For example, if you have a line of slope 1, then the angle it makes is tan^-1(1) = 45 degrees. Most scientific calculators will have an inverse tangent function. Microsoft Excel also has an ATAN(number) function, though it gives the result in radians. You have to convert it to degrees by entering "=+DEGREES(ATAN(1))" for example to get back 45."